The Hunger Games: Catching Fire

Hello, I went to see Hunger Games 2 in the cinema and I heard a beautiful song (to me) that plays three times in the film.
The first time is at the very beginning of the film when Katniss is in the woods, the second roughly in the middle, I can't remember exactly where, and the third time is when Katniss is transported out of the arena with the kind of grapple that is used to collect the bodies of the dead fighters and she looks around as everything collapses around her while being somewhat in a daze.

It's a woman singing, in rather soft and slightly melancholic music; the lyrics she pronounces are something like: oooo oooo oooo.
I did go to check the movie's soundtrack, which has 15 songs, I listened to them all but none match :( So I am turning to you and kindly ask you to please tell me the title of this song if you know it. Thank you for reading my message :D

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